1. Technical Field
The present invention relates to a screen and a screen unit.
2. Related Art
A screen unit known in the art has a screen which reflects light projected from a projection type display apparatus such as a projector for display of an image on the screen. There is disclosed in JP-A-2007-328111, a screen which has a first winding step preventing member and a second winding step preventing member disposed at one and the other ends of the rear surface of the screen, respectively, in the direction perpendicular to the direction where a screen main body and a non-screen body are joined and arranged side by side. Each of the first and second winding step preventing members is located at a position not overlapping with the junction area between a first end and a second end of the two bodies. According to this structure, the screen can be wound for storage with no linear winding wrinkles produced along the step of the junction area between the screen main body and the non-screen body. Thus, the flatness of the screen improves in the condition of use.
In general, under the winding condition of a winding-type screen, the front surface of the screen overlaps with and the rear surface. Thus, when projections or the like are provided on the front surface of the screen so as to allow coating of a projection light reflection film on the front surface, these projections come into contact with the rear surface. In this case, the projections in contact with the rear surface scrape against the rear surface, whereby a part of the projections collapse in their shapes and leave scratches on the external appearance of the reflection film. These scratches on the reflection film adversely affect normal reflection of the light projected from the projector, and cause abnormal display of the image. In addition, in the case of the structure which includes an extension screen base joined to a screen containing a reflection film, similar problems occur due to the contact between the projections and the edge of the junction area.
According to the screen disclosed in JP-A-2007-328111, when the screen is wound, the overlap between the front surface and the rear surface of the screen is avoided in the area of the screen where the first winding step preventing member and the second winding step preventing member are provided. In this case, scraping between the reflection film and the edge of the junction area does not occur. However, in the area where the winding step preventing members are not provided, the front surface and the rear surface of the screen overlap with each other, wherefore similar problems arise.
Generally, in the case of the screen which allows contact between the front surface and the rear surface in the winding condition, the front surface and the rear surface repeatedly contact each other and separate from each other along with the repetitive winding and expanding (draw out) actions of the screen. In this case, the screen is easily made electrostatically charged, and allows dust contained in the use environment to adhere to the front surface and the rear surface of the screen. As a result, the reflectance of the reflection film decreases.
Accordingly, such a screen and a screen unit have been demanded which can protect the area for reflection or transmission of the projection light from damage in the winding condition of the screen.